La Spezia, Liguria's second city, is situated at the centre of a bay that is one of the deepest and best protected on the Italian coast: this is why it was chosen in the nineteenth century as the site for the navy arsenal. The construction of the arsenal radically changed the appearance of the city. Until that time it had basically kept its mediaeval dimensions, which had only been extended slightly in the sixteenth and seventeenth centuries. Today's city not only has a commercial port but also some industries. Worth visiting are the castle of San Giorgio, the church of Santa Maria Assunta and the Lia Museum.